powerpc/eeh: Synchronize recovery in host/guest

When passing through SRIOV VFs to guest, we possibly encounter EEH
error on PF. In this case, the VF PEs are put into frozen state.
The error could be reported to guest before it's captured by the
host. That means the guest could attempt to recover errors on VFs
before host gets chance to recover errors on PFs. The VFs won't be
recovered successfully.

This enforces the recovery order for above case: the recovery on
child PE in guest is hold until the recovery on parent PE in host
is completed.
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/eeh.c

@@ -1548,6 +1548,17 @@ int eeh_pe_get_state(struct eeh_pe *pe)
 	if (!eeh_ops || !eeh_ops->get_state)
 		return -ENOENT;
 
+	/*
+	 * If the parent PE is owned by the host kernel and is undergoing
+	 * error recovery, we should return the PE state as temporarily
+	 * unavailable so that the error recovery on the guest is suspended
+	 * until the recovery completes on the host.
+	 */
+	if (pe->parent &&
+	    !(pe->state & EEH_PE_REMOVED) &&
+	    (pe->parent->state & (EEH_PE_ISOLATED | EEH_PE_RECOVERING)))
+		return EEH_PE_STATE_UNAVAIL;
+
 	result = eeh_ops->get_state(pe, NULL);
 	rst_active = !!(result & EEH_STATE_RESET_ACTIVE);
 	dma_en = !!(result & EEH_STATE_DMA_ENABLED);